Pre-aligning a substrate in a lithographic apparatus, device manufacturing method, and device manufactured by the manufacturing method

ABSTRACT

A method of pre-aligning a substrate in a lithographic apparatus is described. The substrate has at least one alignment mark provided on a side of the substrate. The method includes determining a relationship between a position of the at least one alignment mark, at least part of an edge of the substrate, and a center of the substrate. A substrate support is provided to support a substrate, the substrate support having at least one optical view window at a predetermined location to view a part of the side of the substrate. The substrate is placed on the substrate support on the basis of the relationship to position the at least one alignment mark in the at least one optical view window.

RELATED APPLICATIONS

This Application is a continuation-in-part of U.S. application Ser. No.11/155,885 filed Jun. 20, 2005, the entire contents of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to pre-aligning a substrate in alithographic apparatus, a lithographic apparatus containing an alignmentsystem containing a pre-alignment device configured to perform apre-alignment method, a device manufacturing method, and a devicemanufactured according to the device manufacturing method.

2. Description of the Related Art

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In such a case, a patterning device, which isalternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.,including part of, one, or several dies) on a substrate (e.g., a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Conventional lithographicapparatus include so-called steppers, in which each target portion isirradiated by exposing an entire pattern onto the target portion atonce, and so-called scanners, in which each target portion is irradiatedby scanning the pattern through a radiation beam in a given direction(the “scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

In a manufacturing process using a lithographic projection apparatus, apattern in a patterning device is imaged onto a substrate positioned ona substrate support. The substrate is at least partially covered by alayer of energy-sensitive material (also termed resist). Prior to, andafter this imaging step, the substrate may undergo various procedures,such as a post-exposure bake (PEB), development, a hard bake, andmeasurement and/or inspection of the imaged features. These proceduresare used as a basis to pattern an individual layer of a device, e.g., anintegrated circuit (IC). Such a patterned layer may then undergo variousprocesses such as etching, ion-implantation (doping), metallization,oxidation, chemo-mechanical polishing, etc., all intended to finish offan individual layer. If several layers are required, then the wholeprocedure, or a variant thereof, will have to be repeated for each newlayer. Eventually, an array of devices will be present on the substrate.These devices are then separated from each other by a technique such asdicing or sawing, after which the individual devices can be mounted on acarrier, connected to pins, etc.

Alignment is the process of positioning the image of a specific point onthe patterning device to a specific point on the substrate that is to beexposed. Typically, one or more alignment marks, such as a smallpattern, are provided on each of the substrate and the patterningdevice. As indicated above, a device such as an IC may consist of manylayers that are built up by successive exposures with intermediateprocessing steps. Before each exposure, alignment is performed tominimize any positional error between the new exposure and the previousones, such error being also termed overlay error. A substrate generallymay be provided with alignment marks at both sides of the substrate.

An alignment process involves a pre-alignment procedure in which theedge and the center of a (generally circular) substrate are determined,and an alignment procedure in which the substrate is accurately alignedusing the one or more alignment marks provided on the substrate. After asubstrate has been pre-aligned in a pre-alignment device, the substrateis transferred to a substrate support by a substrate handler, whichusually is a robot having an arm for transferring the substrate from thepre-alignment device to the substrate support.

In a pre-alignment procedure, different devices may be used. In a knownsubstrate pre-alignment procedure, a pre-alignment device is used havinga pre-alignment support provided with mechanical pins abuttingpredetermined edge portions of the substrate. Use of such apre-alignment device presupposes a known diameter of the substrate. Ifthe diameter of the substrate may vary, an offset in the determinationof the orientation of the center of the substrate may be introduced,both in terms of an offset in an X direction, an offset in a Ydirection, and an offset in a φ (angular) direction (where the substrateessentially extends in an X-Y plane, and φ denotes an angle of rotationof the center of the substrate). In fact, the offset defines adifference between the substrate's geometrical coordinate system and acoordinate system based on the alignment marks provided on thesubstrate. The offset may be determined when the diameter of thesubstrate is known. Alternatively, a pre-alignment device may be usedhaving a substrate edge detector relative to which the substrate isrotated on a pre-alignment support of the pre-alignment device. Byrotating the substrate and simultaneously measuring the location of theedge, a center X, Y and φ offset may be determined. As a furtheralternative, a pre-alignment device may be used having a number ofspaced substrate edge detectors located along an expected edge portionof a substrate. No rotation of the substrate is necessary to determine acenter of substrate, although, if the diameter of the substrate mayvary, an X, Y, and φ offset in the determination of the orientation ofthe center of the substrate may be introduced. These offsets may bedetermined when the diameter of the substrate is known.

Once the offset referred to above has been determined, an orientation ofthe particular substrate can be chosen such that the substrate may beplaced correctly on a substrate support to perform an alignmentprocedure.

Following a pre-alignment procedure, in an alignment procedure of asubstrate on a substrate support, the image of an alignment mark on thepatterning device is positioned accurately to an image of an alignmentmark on the substrate.

It is observed that in some technologies, such as micro systemtechnology (MST) and micro electromechanical systems (MEMS), devices arefabricated from both sides of a substrate. Exposures performed on oneside of the substrate must be accurately aligned with featurespreviously exposed on the other side of the substrate.

Throughout this specification, reference to an alignment mark being on aparticular side of the substrate of course includes the alignment markbeing etched into that side of the substrate, and includes the alignmentmark having subsequent material deposited on top of it such that it isembedded and is no longer necessarily exposed at the surface.

U.S. Patent Application Publication No. 2002/0109825 A1, which hereby isincorporated by reference in its entirety, discloses a lithographicapparatus which is provided with an optical system, such as a systememploying one or more laser beams, built into a substrate table forproducing an image of an alignment mark that is provided on the backsideof the substrate, i.e., the side of the substrate which is facing thesubstrate table. The image is located at the plane of the front side ofthe substrate, and can be viewed by an alignment system from the frontside of the substrate. Simultaneous alignment between marks on the backand front of the substrate and a patterning device can be performedusing a pre-existing alignment system.

In a production facility where substrates are processed to yielddevices, lithographic equipment of different suppliers may be used. Thedifferent suppliers generally employ different pre-alignment proceduresto determine the edge and the center of the substrate prior to analignment procedure based on the recognition of one or more alignmentmarks on the substrate. Therefore, unexpected or at least basicallyunknown position deviations of the alignment marks may be encounteredwhen processing substrates on different equipment. Moreover, when usingone or more alignment marks (sometimes also referred to as alignmenttargets) on the backside of a substrate, there is a restriction in thepositioning of such alignment marks. This restriction stems from thelimited physical size of a view window of the optical system used fordetermining the position of the alignment marks. A pre-alignment methodtherefore should be designed to place a substrate on a substrate supportsuch that the alignment marks on the backside of a substrate may beviewed in the view window of the optical system, despite the use oflithographic equipment from different suppliers used to produce specificdevices.

SUMMARY OF THE INVENTION

It is desirable to provide a pre-alignment method and apparatus allowingthe use of equipment from different suppliers while avoiding elaboratepre-alignment processes.

In an aspect of the invention, a method of pre-aligning a substrate in alithographic apparatus is provided, the substrate having at least onealignment mark provided on a side of the substrate, the methodcomprising: determining a relationship between a position of the atleast one alignment mark, at least part of an edge of the substrate, anda center of the substrate; providing a substrate support to support asubstrate, the substrate support having at least one optical view windowat a predetermined location to view a part of the side of the substrate;and placing the substrate on the substrate support on the basis of therelationship to position the at least one alignment mark in the at leastone optical view window.

According to embodiment of the invention, one or more alignment marksare provided on a side of the substrate in a marking apparatus, such asa lithographic apparatus or other suitable apparatus. By determining therelationship between a position of the at least one alignment mark, theedge and the center of the substrate, and using this relationship whenplacing, e.g., by a controllable handling apparatus, the substrate on asubstrate support of a lithographic apparatus with knowncharacteristics, which may be different from those of the markingapparatus, a substrate may be correctly pre-aligned on the substratesupport, with the one or more alignment marks located in a view windowof an alignment system of the lithographic apparatus. The relationshipmay include data indicating a translation and a rotation of a substratearound its center. The data may be stored in, or input to, a controlsystem of the lithographic apparatus.

In another aspect of the invention, a method of pre-aligning a substrateis provided, the method comprising: determining a position of at leastpart of an edge of the substrate, and a center of the substrate;predetermining a relationship between a position of at least onealignment mark, the at least part of the edge of the substrate, and thecenter of the substrate; providing the at least one alignment mark on aside of the substrate on the basis of the relationship; providing, in alithographic apparatus, a substrate support to support a substrate, thesubstrate support having at least one optical view window at apredetermined location to view a part of the side of the substrate; andplacing the substrate on the substrate support to position the at leastone alignment mark in the at least one optical view window of thesubstrate support.

Here, a particular location of the one or more alignment marks may bechosen on the basis of a desired relationship such as to conform to therequirements of a lithographic apparatus in which the substrate is to beprocessed such as to correctly pre-align the substrate on the substratesupport, with the one or more alignment marks located in a view windowof an alignment system of the lithographic apparatus. Again, therelationship may include data indicating a translation and a rotation ofa wafer around its center, now prior to applying the one or morealignment marks.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic projection apparatus according to anembodiment of the invention;

FIG. 2 is a schematic cross-section illustrating a substrate supportaccording for use in the invention;

FIG. 3 is a schematic side view illustrating a pre-alignment deviceaccording to an embodiment of the invention;

FIG. 4 is a schematic top view of the pre-alignment device of FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus includes an illuminationsystem (illuminator) IL configured to condition a radiation beam B(e.g., UV radiation or any other suitable radiation), a mask supportstructure (e.g., a mask table) MT constructed to support a patterningdevice (e.g., a mask) MA and connected to a first positioning device PMconfigured to accurately position the patterning device in accordancewith certain parameters. The apparatus also includes a substrate table(e.g., a wafer table) WT or “substrate support” constructed to hold asubstrate (e.g., a resist-coated wafer) W and connected to a secondpositioning device PW configured to accurately position the substrate inaccordance with certain parameters. The apparatus further includes aprojection system (e.g., a refractive projection lens system) PSconfigured to project a pattern imparted to the radiation beam B bypatterning device MA onto a target portion C (e.g., including one ormore dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The mask support structure supports, i.e., bears the weight of, thepatterning device. It holds the patterning device in a manner thatdepends on the orientation of the patterning device, the design of thelithographic apparatus, and other conditions, such as for examplewhether or not the patterning device is held in a vacuum environment.The mask support structure can use mechanical, vacuum, electrostatic orother clamping techniques to hold the patterning device. The masksupport structure may be a frame or a table, for example, which may befixed or movable as required. The mask support structure may ensure thatthe patterning device is at a desired position, for example with respectto the projection system. Any use of the terms “reticle” or “mask”herein may be considered synonymous with the more general term“patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section so as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.,employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g., employing a programmable mirror array of a typeas referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables or “substrate supports” (and/or two or more masktables or “mask supports”). In such “multiple stage” machines theadditional tables or supports may be used in parallel, or preparatorysteps may be carried out on one or more tables or supports while one ormore other tables or supports are being used for exposure.

As explained above, the lithographic apparatus may also be of a typewherein at least a portion of the substrate may be covered by a liquidhaving a relatively high refractive index, e.g., water, so as to fill aspace between the projection system and the substrate. An immersionliquid may also be applied to other spaces in the lithographicapparatus, for example, between the mask and the projection system.Immersion techniques can be used to increase the numerical aperture ofprojection systems. The term “immersion” as used herein does not meanthat a structure, such as a substrate, must be submerged in liquid, butrather only means that a liquid is located between the projection systemand the substrate during exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDincluding, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may include an adjuster AD configured to adjust theangular intensity distribution of the radiation beam. Generally, atleast the outer and/or inner radial extent (commonly referred to asσ-outer and σ-inner, respectively) of the intensity distribution in apupil plane of the illuminator can be adjusted. In addition, theilluminator IL may include various other components, such as anintegrator IN and a condenser CO. The illuminator may be used tocondition the radiation beam, to have a desired uniformity and intensitydistribution in its cross-section.

The radiation beam B is incident on the patterning device (e.g., maskMA), which is held on the mask support structure (e.g., mask table MT),and is patterned by the patterning device. Having traversed the mask MA,the radiation beam B passes through the projection system PS, whichfocuses the beam onto a target portion C of the substrate W. With theaid of the second positioning device PW and position sensor IF (e.g., aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g., so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioning device PM and another position sensor(which is not explicitly depicted in FIG. 1) can be used to accuratelyposition the mask MA with respect to the path of the radiation beam B,e.g. after mechanical retrieval from a mask library, or during a scan.In general, movement of the mask table MT may be realized with the aidof a long-stroke module (coarse positioning) and a short-stroke module(fine positioning), which form part of the first positioning device PM.Similarly, movement of the substrate table WT or “substrate support” maybe realized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the mask table MT may be connected to ashort-stroke actuator only, or may be fixed. Mask MA and substrate W maybe aligned using mask alignment marks M1, M2 and substrate alignmentmarks P1, P2. Although the substrate alignment marks as illustratedoccupy dedicated target portions, they may be located in spaces betweentarget portions (these are known as scribe-lane alignment marks).Similarly, in situations in which more than one die is provided on themask MA, the mask alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the mask table MT or “mask support” and the substratetable WT or “substrate support” are kept essentially stationary, whilean entire pattern imparted to the radiation beam is projected onto atarget portion C at one time (i.e., a single static exposure). Thesubstrate table WT or “substrate support” is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.

2. In scan mode, the mask table MT or “mask support” and the substratetable WT or “substrate support” are scanned synchronously while apattern imparted to the radiation beam is projected onto a targetportion C (i.e., a single dynamic exposure). The velocity and directionof the substrate table WT or “substrate support” relative to the masktable MT or “mask support” may be determined by the (de-)magnificationand image reversal characteristics of the projection system PS. In scanmode, the maximum size of the exposure field limits the width (in thenon-scanning direction) of the target portion in a single dynamicexposure, whereas the length of the scanning motion determines theheight (in the scanning direction) of the target portion.

3. In another mode, the mask table MT or “mask support” is keptessentially stationary holding a programmable patterning device, and thesubstrate table WT or “substrate support” is moved or scanned while apattern imparted to the radiation beam is projected onto a targetportion C. In this mode, generally a pulsed radiation source is employedand the programmable patterning device is updated as required after eachmovement of the substrate table WT or “substrate support” or in betweensuccessive radiation pulses during a scan. This mode of operation can bereadily applied to maskless lithography that utilizes programmablepatterning device, such as a programmable mirror array of a type asreferred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

FIG. 2 shows a wafer W on a wafer table WT, also termed hereinafter:substrate support. Wafer marks WM1 and WM2 are provided on a side (“backside”) of the wafer W. An optical system is built into the wafer tableWT for providing optical access to the wafer marks WM1, WM2 on the backside of the wafer W. The optical system comprises one arm or a pluralityof arms 10A, 10B. Each arm may consist of two mirrors 12, 14 and twolenses 16, 18. The mirrors 12, 14 in each arm are inclined such that thesum of the angles that they make with the horizontal is 90°. In thisway, a beam of light impinging vertically on one of the mirrors willremain vertical when reflected off the other mirror.

In use, light is directed from above the wafer table WT onto a mirror12, through lenses 16 and 18, onto mirror 14 and then onto therespective wafer mark WM1, WM2. Light is reflected off portions of thewafer mark and returns along an arm of the optical system via mirror 14,lenses 18 and 16, and mirror 12. The mirrors 12, 14 and lenses 16, 18are arranged such that an image 20A, 20B of the wafer mark WM1, WM2 isformed at the plane of the front (top) surface of the wafer W,corresponding to the front side of the wafer W. The order of the lenses16, 18 and the mirrors 12, 14 may be different, as appropriate to theoptical system. For example, lens 18, could be between the mirror 14 andthe wafer W. Also, in an arm any other number of lenses may be used.

It is observed that the arms of the optical system may have differentorientations as seen in a plane parallel to the back side of the waferW, while one end of an arm is situated such that it is below the waferW, and the opposite end of the arm is situated in the area of the wafertable WT not (fully) covered by the wafer W. It is further noted thatthe mirrors 12, 14 of an arm of the optical system need not be providedas discrete components, but may be integral with the wafer table WT. Forthis purpose, appropriate faces may be machined into the wafer table WT,which then may be provided with a coating to improve reflectivity, thusforming the mirrors 12, 14. As a further alternative, the arms of theoptical system may be embodied using optical fibers or coherent opticalfiber bundles, and lenses to couple radiation into and out of thefibers.

An alignment system for performing an accurate alignment (following apre-alignment) may be a through-the-lens (TTL) arrangement, such thatthe lens system PL between the mask MA and the wafer W is actually theprojection lens used for the exposure radiation. However, the alignmentsystem can also be off-axis (OA).

In the method according to an embodiment of the invention, arelationship between the position of at least one alignment mark on asubstrate, at least part of an edge of the substrate, and a center ofthe substrate is to be determined. Such a relationship may be expressedin data which describe an offset between a geometrical coordinate systemand an alignment coordinate system coupled to the at least one alignmentmark. The offset may be expressed in terms of a translation and arotation value. The translation value may be a distance between a centerof the geometrical coordinate system and a center of the alignmentcoordinate system, expressed in an X coordinate and a Y coordinate,where the translation is in a X-Y plane. The rotation value may be anangle of rotation around one of the centers, expressed in an angle ofrotation φ, where at least part of the edge of the substrate (such as anotch or a flat edge part) may determine a reference angle. Thisrelationship may be established in various ways.

One way of determining a relationship between the position of at leastone alignment mark on a substrate, at least part of an edge of thesubstrate, and a center of the substrate may be seen in performingoff-line measurements of the positions on a plurality of substrates,determining an average value of offsets of an X position, a Y positionand an angle of rotation φ of a center of the substrates, and storingthe average offset values for the plurality of substrates. Eachsubstrate will have the same (average) relationship assigned to it.

Instead of determining average values for a plurality of substrates, aspecific set of values X, Y and φ may be determined for each substratein an off-line measurement, coupling each set of values to thecorresponding substrate, which may be identified by a suitableidentifier assigned to it.

An alternative way of determining a relationship between the position ofat least one alignment mark on a substrate, at least part of an edge ofthe substrate, and a center of the substrate may be seen inpredetermining this relationship in terms of a selected set of values X,Y and φ previous to providing an alignment mark on the substrate, andonly then providing the at least one alignment mark on the substrate incorrespondence with the predetermined set of values. This may also beregarded as an off-line procedure.

A further way of determining a relationship between the position of atleast one alignment mark on the substrate, at least part of an edge ofthe substrate, and a center of the substrate may be seen in determininga specific set of values X, Y and φ in an in-line measurement in apre-alignment device of a lithographic apparatus, before an exposure ofthe substrate takes place. When the alignment mark is provided at a side(also called: backside) of the substrate opposite to the exposed side ofthe substrate, the pre-alignment device requires a mark sensorconfigured to capture an image of the alignment mark while the alignmentmark is facing a pre-alignment support. Further details of apre-alignment device are disclosed below.

FIGS. 3 and 4 illustrate a pre-alignment device 30 for performing apre-alignment procedure to be elucidated below. The pre-alignment device30 includes a pre-alignment support 32 for supporting a substrate 33 (inFIG. 4 the substrate is indicated with broken lines), the pre-alignmentsupport 32 being rotatable around an axis 34 such that an angle ofrotation of the pre-alignment support 32 may be measured and controlledin a manner known per se, and not shown or explained in more detail. Thepre-alignment support 32 includes vacuum chambers 36 which are open atthe side facing the substrate 33. By lowering a gas pressure in thevacuum chambers 36 relative to the ambient gas pressure, the substrate33 may be engaged fixedly on the pre-alignment support 32. Thepre-alignment device 30 further includes an arm-shaped translationactuator 38 having a vacuum chamber 40 which is open at a side facingthe substrate 33. The translation actuator 38 is movable in thedirections of double arrow 42 by drive devices known per se, and notshown or explained in more detail. The movement of the translationactuator 38 may be measured and controlled in a manner known per se, andnot shown or explained in more detail. By lowering a gas pressure in thevacuum chamber 40 relative to the ambient gas pressure, the substrate 33may be engaged fixedly on the translation actuator 38 (while at the sametime disengaging the substrate 33 from the pre-alignment support 32) andtranslated as required. On the other hand, the substrate 33 will bedisengaged from the translation actuator while being engaged on thepre-alignment support.

The pre-alignment device 30 further includes an edge sensor 44, e.g.,embodied as a linear CCD (Charge Coupled Device) sensor, mounted on astructure not shown on which also the pre-alignment support 32 ismounted. The edge sensor 44 may optically measure part of the edge ofthe substrate 33 located in a recess of the edge sensor 44. By rotatingthe substrate 33 fixedly engaged on the pre-alignment support 32, apredetermined part of the edge of the substrate 33 may be measured, andfrom the data produced by the edge sensor, a geometrical center of thesubstrate 33 may be determined, as well as the location of a specificedge part such as a notch or a flat edge part (in practice also referredto as ‘flat’).

The pre-alignment device 30 further includes an optical mark sensor 46interacting with an optical device 48. The optical device 48 basicallycorresponds to an optical arm 10A or 10B shown in FIG. 2, and has analignment mark end 50 and a mark sensor end 52. The alignment mark end50 is configured for taking an image of the side of the substrate facingthe pre-alignment support 32. The mark sensor end 52 is configured toprovide the image to the mark sensor 46.

In an embodiment, the alignment mark end 50 of the optical device 48 maybe moved relative to the pre-alignment support 32 in the directions ofdouble arrow 42 to scan a ring-shaped or ring-section shaped area of thebackside of the substrate 33 (when rotating the substrate 33) in orderto locate an alignment mark provided on the backside of the substrate33. In a further embodiment, the optical device 48 may be moved as awhole relative to the pre-alignment support 32 in the directions ofdouble arrow 42 to scan a ring-shaped or ring-section shaped area of thebackside of the substrate 33 (when rotating the substrate 33) in orderto locate an alignment mark provided on the backside of the substrate33. In a further embodiment, the mark sensor 46 may be moved relative tothe optical device 48 in the directions of double arrow 42 to scan aring-shaped or ring-section shaped area of the backside of the substrate33 (when rotating the substrate 33) in order to locate an alignment markprovided on the backside of the substrate 33. In a further embodiment, acombination of two or three of these movements may be established. Inany of these movements, the position of the moving part is measured andcontrolled.

With the measurements made by the edge sensor 44, and the combination ofthe mark sensor 46 and the optical device 48, a relationship between theposition of at least one alignment mark on (the backside of) thesubstrate 33, at least part of an edge of the substrate 33, and a centerof the substrate 33 may be determined, and may be expressed in a set ofoffset values X, Y, and φ for the particular substrate 33, where thesubstrate extends in an X-Y plane, and axis 34 is an axis of rotation.

In a formula, a substrate center offset Δx, Δy of a substrate having adiameter D_(w) may be expressed as $\begin{pmatrix}{\Delta\quad x} \\{\Delta\quad y}\end{pmatrix} = {{\left( {D_{W} - D_{n}} \right)*\begin{pmatrix}a \\b\end{pmatrix}} + \begin{pmatrix}e \\f\end{pmatrix}}$where D_(n) is a normalization constant, and a, b, e, and f are processparameters being a function of the used lithographic apparatus. In casea substrate is used with a substrate reference side part (notch orflat), the substrate center offset Δx, Δy of a substrate having adistance d_(w) between the reference side part and the wafer center, maybe expressed as $\begin{pmatrix}{\Delta\quad x} \\{\Delta\quad y}\end{pmatrix} = {{\left( {d_{W} - d_{n}} \right)*\begin{pmatrix}c \\d\end{pmatrix}} + \begin{pmatrix}e \\f\end{pmatrix}}$where d_(n) is a normalization constant, and c, d, e, and f are processparameters being a function of the used lithographic apparatus. Thenormalization constants D_(n) and d_(n) are size values of a calibrationor normalization substrate.

Subsequently, a desired orientation of the substrate 33 may beestablished by the pre-alignment device 30 while the substrate still issupported in the pre-alignment device 30, before a transfer of thesubstrate from the pre-alignment support 32 to the substrate support WTtakes place, such that the at least one alignment mark will bepositioned in the at least one optical view window of the substratesupport. In this process, a control device is used to control an angleof rotation of the pre-alignment support 32, and a translation of thetranslation device 38 on the basis of measurements from the edge sensor44 and the mark sensor 46. To reach a desired orientation in thepre-alignment device 30, the translation actuator 38 may be used toprovide a required translation, and the pre-alignment support 32 may beused to provide a required rotation. This procedure allows for atransfer using a simple transfer structure, such as a pick and placerobot (not shown in detail).

Further, the substrate 33 may be transferred by the transfer structurefrom the pre-alignment device 30 to the substrate support WT withoutfirst establishing a desired orientation of the substrate 33. In thissituation, the desired orientation is established by the transferstructure after taking the substrate 33 from the pre-alignment device30, and before bringing the substrate 33 into contact with the substratesupport WT such that the at least one alignment mark is positioned inthe at least one optical view window of the substrate support. Thisprocedure requires a transfer structure configured to set a desiredorientation during the transfer of the substrate 33 from thepre-alignment device 30 to the substrate support WT.

Substrates produced on an apparatus of one supplier may be processed onan apparatus of a different supplier using the pre-alignment method anddevice according to embodiments of the present invention.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion,” respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

Although specific reference may have been made above to the use ofembodiments of the invention in the context of optical lithography, itwill be appreciated that the invention may be used in otherapplications, for example imprint lithography, and where the contextallows, is not limited to optical lithography. In imprint lithography atopography in a patterning device defines the pattern created on asubstrate. The topography of the patterning device may be pressed into alayer of resist supplied to the substrate whereupon the resist is curedby applying electromagnetic radiation, heat, pressure or a combinationthereof. The patterning device is moved out of the resist leaving apattern in it after the resist is cured.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.,having a wavelength of or about 365, 248, 193, 157 or 126 nm) andextreme ultra-violet (EUV) radiation (e.g., having a wavelength in therange of 5-20 nm), as well as particle beams, such as ion beams orelectron beams.

The term “lens,” where the context allows, may refer to any one orcombination of various types of optical components, includingrefractive, reflective, magnetic, electromagnetic and electrostaticoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the invention may take the form of acomputer program containing one or more sequences of machine-readableinstructions describing a method as disclosed above, or a data storagemedium (e.g., semiconductor memory, magnetic or optical disk) havingsuch a computer program stored therein.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1. A method of pre-aligning a substrate in a lithographic apparatus, thesubstrate having an alignment mark provided on a backside of thesubstrate, the method comprising: determining a relationship between aposition of the alignment mark, at least part of an edge of thesubstrate, and a center of the substrate; and placing the backside ofthe substrate on a substrate support on the basis of said relationshipto position the alignment mark in an optical view window of thesubstrate support, the optical view window arranged in the substratesupport at a predetermined location to view a part of the backside ofthe substrate.
 2. The method of claim 1, wherein following saiddetermining, and prior to said placing, the substrate is repositioned onthe basis of said relationship.
 3. The method of claim 2, wherein saiddetermining is performed in a pre-alignment device, and thepre-alignment device is configured to reposition the substrate on thebasis of said relationship.
 4. The method of claim 1, wherein in saiddetermining, the edge of the substrate and at least part of saidbackside of the substrate containing the alignment mark is scanned. 5.The method of claim 4, wherein the determining includes rotating thesubstrate.
 6. The method of claim 1, wherein said relationship includesa translation and a rotation value.
 7. The method of claim 1, whereinsaid relationship is determined as an average for a plurality ofsubstrates.
 8. The method of claim 1, wherein the determining includesmeasuring an edge of the substrate to determine a geometrical center ofthe substrate.
 9. The method of claim 1, wherein the determiningincludes rotating the substrate and scanning the backside of thesubstrate along a radial direction of the substrate to locate a positionof the alignment mark.
 10. The method of claim 9, wherein the scanningincludes imaging the backside of the substrate.
 11. A lithographicapparatus comprising: a radiation system to configure a beam ofradiation; a patterning support to support a patterning structure topattern the beam of radiation according to a desired pattern; asubstrate support to support a substrate, the substrate support havingan optical view window at a predetermined location to view a part of abackside of the substrate; a projection system to project the patternedbeam of radiation onto a target portion of the substrate; an alignmentsystem to align a pattern of the patterning structure with an alignmentmark provided on the backside of the substrate, using alignmentradiation, the alignment system comprising a pre-alignment deviceconfigured to: (a) determine a relationship between a position of thealignment mark, at least part of the edge, and a center of thesubstrate; and (b) place the substrate on the substrate support on thebasis of said relationship to position the alignment mark in the opticalview window.
 12. The apparatus of claim 11, further comprising anoptical system to transmit an image of the alignment mark from thebackside of the substrate opposite the target portion for use by thealignment system.
 13. A device manufacturing method comprising: (a)determining a relationship between a position of an alignment markprovided on a backside of a substrate, at least part of an edge of thesubstrate, and a center of the substrate; (b) placing the backside ofthe substrate on a substrate support on the basis of said relationshipto position the alignment mark in an optical view window of thesubstrate support, the optical view window arranged in the substratesupport at a predetermined location to view a part of the backside ofthe substrate; (c) transmitting an image of the alignment mark from thebackside side of the substrate for use in an aligning; and (d) aligningthe image of the alignment mark with a pattern of a patterning structureused in projecting a patterned beam of radiation onto a target area of alayer of radiation-sensitive material on a front side of the substrateopposite the backside.
 14. A pre-alignment device configured topre-align a substrate in a lithographic apparatus, the substrate havingan alignment mark provided on a backside of the substrate, thepre-alignment device comprising: a rotatable pre-alignment support tosupport the substrate; an edge sensor to measure at least part of anedge of the substrate; a mark sensor and an optical device to measure aposition of the alignment mark located on the backside of the substratethat faces the pre-alignment support; a control device to control anangle of rotation of the pre-alignment support and a translation of thesubstrate on the basis of measurements from the edge sensor and the marksensor.
 15. The pre-alignment device of claim 14, further comprising atranslation device to translate the substrate.
 16. The pre-alignmentdevice of claim 15, wherein the pre-alignment support has an axis ofrotation, and wherein at least one of the mark sensor and the opticaldevice or a part thereof is movable radially relative to the axis ofrotation.
 17. A lithographic apparatus comprising: a radiation system toconfigure a beam of radiation; a patterning support to support apatterning structure to pattern the beam of radiation according to adesired pattern; a substrate support to support a substrate, thesubstrate support having an optical view window at a predeterminedlocation to view a part of a backside of the substrate; a projectionsystem to project the patterned beam of radiation onto a target portionof the substrate; an alignment system to align a pattern of thepatterning structure with an alignment mark provided on the backside ofthe substrate, using alignment radiation, the alignment systemcomprising a pre-alignment device that includes a rotatablepre-alignment support to support the substrate; an edge sensor tomeasure at least part of an edge of the substrate; a mark sensor and anoptical device to measure a position of the alignment mark located onthe backside of the substrate that faces the pre-alignment support; acontrol device to control an angle of rotation of the pre-alignmentsupport and a translation of the substrate on the basis of measurementsfrom the edge sensor and the mark sensor.
 18. The apparatus of claim 17,further comprising a translation device to translate the substrate. 19.The apparatus of claim 17, wherein the pre-alignment support has an axisof rotation, and wherein at least one of the mark sensor and the opticaldevice or a part thereof is movable radially relative to the axis ofrotation.